The present invention relates generally to medical electrophysiology systems, and specifically to invasive medical probes that may be used to map the electrical activity of the heart.
Cardiac catheters comprising electrophysiological sensors are known for mapping the electrical activity of the heart. Typically the time-varying electrical potentials in the endocardium are sensed and recorded as a function of position inside the heart, and then used to map the local electrogram or local activation time. Activation time differs from point to point in the endocardium due to the time required for conduction of electrical impulses through the heart muscle. The direction of this electrical conduction at any point in the heart is conventionally represented by an activation vector, which is normal to an isoelectric activation front, both of which may be derived from a map of activation time. The rate of propagation of the activation front through any point in the endocardium may be represented as a velocity vector.
Mapping the activation front and conduction fields aids the physician in identifying and diagnosing abnormalities, such as ventricular and atrial tachycardia and ventricular and atrial fibrillation, that result from areas of impaired electrical propagation in the heart tissue. Localized defects in the heart""s conduction of activation signals may be identified by observing phenomena such as multiple activation fronts, abnormal concentrations of activation vectors, or changes in the velocity vector or deviation of the vector from normal values. Furthermore, there may be no electrical propagation at all within defective portions of the heart muscle that have ceased to function, due to local infarction, for example. Once a defect is located by such mapping, it may be ablated (if it is functioning abnormally) or otherwise treated so as to restore the normal function of the heart insofar as is possible.
Mapping of the electrical activation time in the heart muscle requires that the location of the sensor within the heart be known at the time of each measurement. Such mapping may be performed using a single movable electrode sensor inside the heart, which sensor measures activation time relative to a fixed external reference electrode. This technique, however, gives maps of low resolution and relatively poor accuracy, limited by the accuracy of determination of the position of the electrode at the time of each measurement. The natural movement of the heart makes it very difficult to maintain an accurate reading of the position of the moving electrode from beat to beat. Mapping of electrical activation time using a single electrode is, furthermore, a lengthy procedure, which must generally be performed under fluoroscopic imaging, thereby exposing the patient to undesirable ionizing radiation. Further, in an arrhythmic heart, activation times at a single location may change between consecutive beats.
Because of these drawbacks of single-electrode mapping, a number of inventors have taught the use of multiple electrodes to measure electrical potentials simultaneously at different locations in the endocardium, thereby allowing activation time to be mapped more rapidly and conveniently, as described, for example, in PCT patent publication WO 95/05773, whose disclosure is incorporated herein by reference. In this case, the positions of all the electrode sensors must be determined at the time of measurement, typically by means of fluoroscopic or ultrasonic imaging. These methods of position determination, however, are complicated, inconvenient and relatively inaccurate, therefore limiting the accuracy of mapping.
Alternatively, U.S. Pat. Nos. 5,471,982 and 5,465,717, whose disclosures are incorporated herein by reference, teach the use of an electrode basket, which is inserted into a chamber of the heart and then expanded so that a plurality of electrodes are simultaneously brought into contact with multiple points on the endocardium. The relative electrical activation times at all the electrodes may then be measured simultaneously and used to detect and localize abnormalities. The basket is of limited usefulness in creating high-resolution maps of the electrical activation vector, however, because it cannot easily be repositioned once it is expanded inside the heart, and furthermore, determining the absolute positions of the electrodes requires the use of fluoroscopy or other painstaking and undesirable imaging methods. Further, the basket catheter does not contract with the heart, so the electrodes in the basket catheter cannot maintain contact with the same portion of the myocardium for the entire cycle, and the electrodes may not return to the same position relative to the myocardium for each cycle.
U.S. Pat. No. 5,487,391, to Panescu, for example, describes a multiple electrode probe for deployment inside the heart. Signals received from the multiple electrodes are used for deriving the propagation velocity of depolarization events. This patent makes no provision, however, for independently determining the positions of the electrodes relative to an external or heart-fixed frame of reference, and the velocity is derived relative to the probe, rather than to the heart itself.
Detecting the position in space of a single electrophysiology mapping electrode is described, inter alia, in PCT patent application number PCT/US95/01103, filed Jan. 24, 1995, U.S. provisional application 60/009,769, filed Jan. 11, 1996, U.S. patent application Ser. No. 08/595,365, filed Feb. 1, 1996, both titled xe2x80x9cCardiac Electromechanicsxe2x80x9d, and U.S. Pat. No. 5,391,199, issued Feb. 21, 1995, the disclosures of all of which are incorporated herein by reference.
U.S. Pat. No. 5,450,846, whose disclosure is incorporated herein by reference, describes a catheter, which may be easily repositioned inside the heart, comprising an ablator at its distal tip and pairs of non-contacting sensing electrodes arrayed around the outside of the catheter near the distal end. Each electrode senses local electrogram signals generated in the endocardium in a small area near the side of the catheter that it faces. Differences in the activation times in the signals sensed by the pairs of electrodes are used to estimate the direction of the activation vector in the vicinity of the catheter, so as to guide the operator in positioning the ablator. However, use of this device in high-resolution mapping of activation vectors is not practical either, because of the difficulty of determining the absolute position of the catheter tip, which must be performed by imaging methods, and because of the inferior accuracy of the non-contact electrogram measurement.
PCT publication WO/ 95/10226 describes a catheter that includes a ring at its distal end, designed to bear against the circumference of a valve of the heart. The ring comprises electrodes, which measure electrical activity in the valve tissue. When abnormal electrical activity is detected in the valve tissue adjacent to one of the electrodes, an electrical current is applied through the electrode so as to ablate the tissue at the site of the abnormal activity. The invention provides no means for determination of the position of the ring and electrodes, however, other than methods of imaging known in the art, and is therefore not useful for mapping electrical activity, nor is it useful in areas of the heart other than the valves.
U.S. Pat. No. 5,555,883, to Avitall, the disclosure of which is incorporated herein by reference, describes a catheter with a loop shaped mapping and ablation system. There is no provision, in this patent, for determining the position of individual electrodes relative to the heart surface being mapped/ablated.
It is an object of the present invention to allow simultaneous measurement of physiological signals by multiple sensors inside a human body, while simultaneously providing accurate measurement of at least the relative locations of all the sensors.
In one aspect of the invention, the sensors are fixed to a catheter, and the locations of the sensors arc measured by determining the position of a device in the catheter that generates position and orientation information.
A further object of the present invention is to provide a method and a device for rapidly and accurately measuring local electrical propagation vectors in the heart muscle, in order to locate sites of abnormal electrical propagation, for purposes of subsequent diagnosis and therapy.
In a preferred embodiment of the present invention, a plurality of electrodes are attached to a structure at the distal end of a catheter. One or more devices for generating position information are placed in proximity to the electrodes, so that the positions of all the electrodes can be determined in relation to an external frame of reference or relative to the heart. The position information and signals measured by the electrodes are used to determine the direction and magnitude of the electrical activation vector at the location of the structure at the distal end of the catheter.
In preferred embodiments of the present invention, the structure at the distal end of the catheter comprises at least three non-collinear electrodes, so that the direction of the electrical activation vector in the plane defined by the electrodes may be fully determined.
In some preferred embodiments of the present invention, the electrodes are attached to a substantially rigid ring at the distal end of a catheter. A device that generates position information is coupled to the ring, so that the position and rotational orientation of the ring may be determined, thus determining the locations of all the electrodes. Alternatively or additionally, the geometrical shape and angular orientation of the ring are known relative to the catheter. If the locations of the electrodes relative to the catheter are substantially predetermined, the positions of all the electrodes may be determined from a determined position and orientation of the catheter tip. Further, in this case, it is sufficient to determine the location of the tip and only the rotational coordinate of the catheter tip around its axis.
A catheter of the present invention is preferably inserted into a chamber of the heart. The ring at the distal end of the catheter is placed in contact with the endocardium, and the electrical propagation vector is measured at the location of the ring. The distal end of the catheter may then be repeatedly repositioned to other locations on the endocardium, so as to generate a map of the propagation vector field or to locate an area of abnormality.
In the context of this invention, the term substantially rigid, as applied to the ring at the distal end of the catheter, is taken to mean, that during successive measurements of electrophysiological signals by the electrodes, the shape of the ring and its angular orientation relative to the long axis of the catheter remain fixed in a known, predetermined relation. Consequently, the location of each of the electrodes on the ring relative to a coordinate information device is fixed and known, and thus the locations of all the electrodes relative to an external reference frame may be determined using the location and orientation information provided by the coordinate information device. However, in some embodiments of the invention, where individual electrodes are fixed to the myocardium, such as when using extendible barbs to hold the electrodes in place, the electrodes are allowed to move relative to each other, as a result of myocardial contraction.
Although the substantially rigid ring maintains its shape during measurements, for purposes of insertion and removal of the catheter the ring may be straightened or flattened, so as to pass easily through narrow channels, such as blood vessels, or through a lumen of the catheter.
In a preferred embodiment of the present invention, the substantially rigid ring is formed of a resilient, super-elastic material, such as NiTi. For insertion or removal of the catheter from the body, the ring is compressed inside a narrow sleeve adjacent to the distal end of the catheter. After insertion of the catheter, the ring is ejected from the sleeve and assumes its predetermined shape and position.
In one preferred embodiment of the invention, the substantially rigid ring is made from a flat, ribbon-like section of resilient material. The distal end of the catheter, with which the ring is in contact after it has been ejected from the sleeve, is likewise flat and includes a slot necessary for ejection of the ring. Thus once the ring is ejected, it is substantially prevented from rotating or tilting relative to the axis of the catheter and does not substantially bend or deform under the forces exerted on it during successive measurements inside the heart. In this manner the positions of the electrodes on the ring are maintained in predetermined relations to the distal end of the catheter.
In another preferred embodiment of the present invention, the ring is formed of a hollow section of resilient, superelastic material, which is rigidly coupled to the distal end of the catheter at a known angular orientation. For insertion or removal of the catheter from the body, the ring is straightened by insertion of a stylette into the lumen of the hollow section. After insertion of the catheter into the heart, the stylette is withdrawn, and the ring reassumes its predetermined shape and orientation.
In an alternative preferred embodiment of the present invention, the ring at the distal end of the catheter is formed of a hollow section of flexible material, which is straightened for insertion or removal of the catheter from the body by insertion of a straight stylette into the lumen of the hollow section. After the straight stylette is withdrawn, a second stylette, formed of substantially rigid, resilient material and including a curved portion at its distal end, is inserted. For insertion of this second stylette through a lumen of the catheter, the curved distal portion of the stylette is straightened, and the relative stiffness of the catheter causes the stylette to remain straight. When this stylette reaches the hollow, flexible section at the distal end of the catheter, however, the resilience of the stylette causes its distal portion to resume its curved shape, and thus causes the hollow, flexible section of the catheter to curve, as well, into the desired ring shape.
In some preferred embodiments of the present invention in which the distal end of the catheter is straightened during insertion into the heart, when the section at the distal end of the catheter is caused to curve into a ring shape after insertion, the distal tip of this section engages a socket in the side of the catheter. Fluoroscopy or other methods of imaging known in the art may be used to observe the ring at the distal end of the catheter and verify that the distal tip of the distal section has engaged the socket, so as to ensure that the ring has assumed its desired shape and orientation prior to beginning electrophysiological measurements.
Alternatively, in some preferred embodiments of this type, the distal tip of the distal end section of the catheter comprises a first electrical contact, and the socket in the side of the catheter comprises a second electrical contact. When the distal tip engages the socket, the first electrical contact is brought into proximity with the second electrical contact. The mutual proximity of the contacts is measured electrically using methods known in the art, so as to verify that the distal tip has engaged the socket.
In other preferred embodiments of the present invention, the structure to which the electrodes are attached at the distal end of the catheter may comprise a ring of any desired cross-sectional profile, or the structure may be formed in a shape of non-uniform profile. In one such preferred embodiment, the structure comprises rigid sections, to which the electrodes are attached, and flexible, resilient sections between the rigid sections. The flexible, resilient sections allow the structure to be easily collapsed for passage through the blood vessels, and then cause the structure to resume its desired shape for making measurements when released inside a chamber of the heart.
In still other preferred embodiments of the present invention, the structure to which the electrodes are attached at the distal end of the catheter is polygonal, most preferably triangular with sharp vertices. When the sharp vertices of the polygonal structure are brought into contact with the endocardium, they will typically lodge in small crevices in the heart tissue, thus preventing the structure from moving during measurement, despite the natural motion of the heart. The electrodes are preferably at the vertices.
In other preferred embodiments of the present invention, the structure in which the electrodes are placed at the distal end of the catheter comprises multiple arms, wherein electrodes are fixed to the arms. During insertion of the catheter into the heart, the arms are held parallel and adjacent to the long central axis of the catheter. Once inside the heart, the arms spread apart, away from the long axis of the catheter at predetermined, known angles.
In one such embodiment of the present invention, each arm is formed of at least two sections of substantially rigid material, connected together by a resilient joint. The arms are joined at their proximal ends to the distal end of the catheter. A draw-wire passes through a lumen in the catheter and is attached at its distal end to the distal ends of the arms, which are joined together. During insertion of the catheter into the heart, the resilient joints tend to hold the arms straight and parallel to the long central axis of the catheter. Once the arms are wholly inside the heart, the draw-wire is pulled back toward the proximal end of the catheter, thereby drawing in the distal ends of the arms and causing the arms to flex at their resilient joints. The draw-wire is pulled back until the joints are completely flexed, and the distal ends of the arms are brought into close proximity with the proximal ends thereof, so that the arms protrude laterally out from the long central axis of the catheter. For removal of the catheter from the heart, the draw-wire is released, and the resilient joints straighten to their original shapes.
In another such embodiment of the present invention, substantially rigid arms, having electrodes adjacent to their distal ends, are contained inside a lumen of the catheter during insertion of the catheter into the heart. Once the distal end of the catheter has been inserted into the heart, the distal ends of the arms are ejected through small radial openings, spaced around the axis of the catheter. The resilience of the arms causes them to spread apart radially away from the long central axis of the catheter and axially, distal to the distal end of the catheter.
In yet other preferred embodiments of the invention, the structure at the distal end of the catheter is a balloon or another inflatable structure, to which electrodes are fixed. After the catheter has been inserted into the heart, the structure is inflated and assumes a predetermined, known shape and orientation relative to the distal end of the catheter.
In some preferred embodiments in accordance with the present invention, the device that generates position information comprises a plurality of coils, as disclosed in PCT patent application number PCT/US95/01103, filed Jan. 24, 1995, which is assigned to the assignee of the present application and whose disclosure is incorporated herein by reference. This device continuously generates six-dimensional position and orientation information regarding the catheter tip. This system uses a plurality of non-concentric coils adjacent to a locatable site in the catheter, for example near its distal end. These coils generate signals in response to externally applied magnetic fields, which allow for the computation of six location and orientation coordinates, so that the location and orientation of the catheter in the heart are known without the need for simultaneous imaging, by fluoroscopy or ultrasound, for example. This device generates position information relative to a reference frame defined by field generator coils. In a preferred embodiment of the invention, a Carto system, available from Biosense LTD., Tirat Hacarmel, Israel, is used for determining the position of a catheter.
Other preferred embodiments of the present invention comprise one or more devices for generating three-dimensional location information, as described, for example, in U.S. Pat. No. 5,391,199, to Ben-Haim, and PCT patent application PCT/US94/08352, which are assigned to the assignee of the present application and whose disclosures are incorporated herein by reference. One or more devices for generating location information are placed in the catheter or in the structure containing the electrodes, in proximity to the electrodes. Location information generated by these devices is used to determine the positions of the electrodes.
In one such preferred embodiment of the present invention, two or more devices for generating three-dimensional location information are placed in known, mutually-spaced locations in the catheter or in the structure containing the electrodes, thereby allowing the positions of the electrodes in the structure to be determined.
The device disclosed in the aforementioned ""539 patent application for generating three-dimensional location information preferably comprises a single coil. In preferred embodiments of the present invention that include a device of this type, the coil is toroidal in shape and coaxial with the long, central axis of the catheter. These embodiments thus have the advantage that the catheter may have one or more lumens, which pass through the opening at the center of the toroidal coil, while maintaining a relatively small external catheter diameter.
In some preferred embodiments of the present invention, a device, such as described above, for generating three-dimensional location information is placed in the catheter adjacent to the electrodes and is used to determine the location of the catheter inside the heart. One or more rotation measuring devices measure the angular orientation of the distal end of the catheter. Since the structure in which the electrodes are placed allows the positions and orientations of the electrodes to be known relative to the distal end of the catheter, the location information generated by the location generating device in the catheter, taken together with the measured angular orientation of the catheter, is sufficient to fully determine the locations of the electrodes in the heart.
The rotation measuring device of this embodiment may be of any suitable type known in the art. For example, shaft encoder devices adjacent to the proximal end of the catheter may be used to measure the angle of rotation of the catheter about its long central axis and/or the angle of deflection of the catheter""s distal tip. This embodiment of the invention is especially useful when the path of the catheter is relatively straight.
In some preferred embodiments of the present invention, used for mapping the electrical activity of the heart, two catheters are inserted into the heart. A first catheter comprises a ring with electrodes and a device that generates position information, as described above. A second catheter comprises a device that generates position information, and is positioned in a predetermined location in a chamber of the heart, preferably at the apex of the heart. This second catheter thus allows a reference frame to be defined that is substantially fixed with respect to the heart, relative to which the position of the first catheter is determined, so that errors in position determination due to motion of the heart and the chest, due to breathing, for example, may be canceled.
In a preferred embodiment of the present invention, for use in diagnosing and treating defects in the heart""s electrical conduction, the distal end of the catheter is placed in proximity to the suspected site of a defect. On the basis of the vector direction and magnitude of the electrical impulse flow vector measured at this initial site, the catheter is then moved toward the suspected defect. This procedure is repeated until the catheter reaches the site of the defect. Preferably once the defect is located by the above procedure, it is ablated or otherwise treated by methods known in the art.
While the above preferred embodiments have been described with reference to measurement of electrophysiological signals in the heart, other preferred embodiments of the present invention may be used to measure and map electrical signals in the brain or in other physiological structures.
Furthermore, in other preferred embodiments of the present invention, other sensors, such as ionic sensors, may be used instead of the electrodes to perform localized measurements and map other aspects of physiological activity.
It is another object of some embodiments of the present invention to provide a method for accurately and rapidly determining the magnitude and direction of a vector corresponding to the propagation of activity in physiological tissue.
In one aspect of the present invention, the activity is electrical activity in the heart of a subject, and the vector corresponds to the local velocity of an electrical activation signal. In other aspects of the present invention, the vector corresponds to an ionic current caused by repolarization of the heart tissue, or to currents associated with other elements of the cardiac cycle.
In other aspects of the present invention, the activity is ionic activity or mechanical activity, such as contraction of muscle tissue, and the vector corresponds to the local ionic or isotonic current, respectively.
In a further aspect of the present invention, the magnitude and direction of the vector are determined at a plurality of known locations, and are used to generate a map of the vector as a function of location and/or as a function of time.
In preferred embodiments of the present invention, a plurality of electrodes are placed in known positions adjacent to a location in the endocardium. Electrical signals received from the plurality of electrodes are used to determine local activation times at the respective positions thereof. A local velocity vector is then calculated by comparison of the relative values of the local activation time at the positions of the electrodes.
In preferred embodiments of the present invention, the plurality of electrodes comprises at least three electrodes. The local velocity vector is determined by finding velocity vector components along two non-parallel axes, wherein each of the axes is defined by a pair of the electrodes. Vector arithmetic operations are applied to the velocity vector components to find the direction and magnitude of the local velocity vector.
In preferred embodiments of the present invention, the velocity vector component along each of the axes defined by a pair of electrodes is found by dividing the distance between the electrodes by the difference in their activation times. However, if the difference in activation times between a first pair of electrodes is substantially zero, while the difference in activation times between a second pair of electrodes is not zero, then the local velocity vector is found to be perpendicular to the axis defined by the first pair of electrodes. If all the electrodes have substantially the same activation time, then the local velocity vector is found to be zero, and the location in the endocardium to which the electrodes are adjacent is determined to contain a suspected site of pathology, for example, a sink or source of local electrical activation.
In preferred embodiments of the present invention, the local velocity vector is mapped at a plurality of locations in the heart by placing the electrodes at the plurality of locations in succession, and determining the local velocity vector at each location. Preferably the mapping of the local velocity vector is used to determine locations of defects in the propagation of electrical activation in the endocardium, and particularly to find sources and sinks of the activation.
Although preferred embodiments of the present invention are described with reference to certain types of catheter and position-sensing apparatus, it will be understood that the inventive principles of the present invention will be equally applicable to other types of probes and to other apparatus and methods, such as ultrasound or fluoroscopic imaging, for determining the positions of sensors attached to the probes.
Alternatively, the inventive principles of the present invention may be applied to measure a local velocity vector without determining the positions or orientations of sensors used in the measurement relative to an external frame of reference. This measurement is useful, for example, in identifying local conduction defects. On the basis of the vector direction of the electrical impulse flow vector measured at an initial site, the catheter is then moved toward the suspected defect. This procedure is repeated until the catheter reaches the site of the defect. Preferably once the defect is located by the above procedure, it is ablated or otherwise treated by methods known in the art.
It will further be understood that although preferred embodiments of the present invention are described with reference to measurement and mapping of electrical activation in the endocardium, the inventive principles of the present invention will be equally applicable to measurement and mapping of the propagation of other signals in the heart, such as isotonic currents and injury currents, as are known in the art. Similarly, these inventive principles may be applied to measurement and mapping of other physiological signals, such as those arising from electrical activity in the brain, or signals received from ionic sensors.
Another aspect of the present invention relates to a soft tip catheter, which may be safely and easily inserted into a body vessel. This catheter of the present invention preferably includes a resilient cap member extending distally from a distal end of the catheter. The resilient cap member preferably includes a tuft of at least one distally extending, resilient lobe with a soft, smooth outer surface or surfaces, preferably constructed of an elastomeric material, such as rubber, latex or silicon-rubber. The cap may be an attachment to the catheter or may be formed as an extension of the catheter material.
Preferably at least one sensor is fixed to the resilient cap member, preferably at the at least one lobe. The sensors may be any type of sensor useful in sensing a physiological activity, for example, determining location and orientation of a tumor, or determining proper functioning of a heart, such as contraction time of a heart muscle, or sensing an activation signal of a heart muscle. Preferably, each lobe also includes apparatus for fixing the lobe to the myocardium, for example, an extendible barb, a lumen attached to an external vacuum pump, or a bump in the external surface of the lobe and which engages local irregularities in the heart muscle.
As the catheter is inserted into a body vessel in a distal direction, the resilient cap member and its lobes may be resiliently inverted over the distal end of the catheter. The resilient inversion of resilient cap member greatly facilitates insertion of the catheter into the vessel, and provides a high degree of insertion safety, thereby substantially eliminating the possibility of the catheter scraping an inner surface of the vessel. The cap and lobes may also be inverted by if they collide with an obstruction as a result of the distal movement of the catheter. The resilient cap member also substantially prevents accidentally puncturing, scraping or otherwise damaging the interior surfaces of a body organ.
In a preferred embodiment of the invention, the catheter includes a position sensor at the base of the tuft, for determining the position of the catheter tip. Preferably, each of the sensors on the tufts has a known position relative to the position sensor. Thus, if the position sensor provides both position and orientation information, the relative positions of all the sensors can be determined. In a preferred embodiment of the invention, the tufts are arranged so that small changes in the positions of the tuft relative to the base (for example, as a result of forward pressure) do not substantially change the relative positions of the tufts.
In a preferred embodiment of the invention, there are no sharp comers or crevasses between the tufts, so that no blood can collect and clot there.
There is therefore provided, in accordance with a preferred embodiment of the present invention, elongate probe apparatus for insertion into the body of a subject, including a structure having a substantially rigid configuration; a plurality of physiological sensors, which generate signals responsive to a physiological activity, the sensors having substantially fixed positions on the structure in the substantially rigid configuration; and one or more devices that generate position signals indicative of the positions of the physiological sensors on the structure in the substantially rigid configuration.
Preferably, the elongate probe comprises a distal end, which is inserted into the body of the subject, wherein the structure, which preferably is made of resilient material, or more preferably superelastic material, has a known shape and orientation in its substantially rigid configuration relative to the distal end of the probe.
Preferably the structure has the shape of a ring in its substantially rigid configuration, and the sensors are mutually spaced around the circumference of the ring. The structure may be made of a flat strip, formed into a ring.
Alternatively, the structure may include a hollow tube. Preferably the tube is formed of flexible material, and the structure further includes a curved stylette, insertable into the center of the hollow tube so as to cause the hollow tube to assume a curved shape.
Alternatively, the structure may have a polygonal shape, preferably triangular, in its substantially rigid configuration. Preferably the sensors are adjacent to the vertices of the structure in its substantially rigid configuration.
In other preferred embodiments of the present invention, the structure includes a multiplicity of arms, such that when the structure is in its substantially rigid configuration, the arms spread radially outward relative to an axis parallel to the long dimension of the elongate probe.
Preferably the arms include substantially rigid segments, which are coupled by resilient joints. Flexure of the joints causes the arms to spread radially outward in the substantially rigid configuration of the structure
Alternatively, the elongate probe includes mutually spaced radial openings in its outer surface, and the arms protrude from the probe through the openings.
In other preferred embodiments of the present invention, the structure further includes an inflatable element, preferably a balloon. Inflation of the inflatable element causes the structure to assume a substantially rigid configuration. Preferably the structure further includes flexible, non-extensible wires.
Preferred embodiments of the present invention further provide that when the structure is in its substantially rigid configuration, the positions of the sensors on the structure define a plane, with a first axis perpendicular to this plane; and the elongate probe defines a second axis parallel to its long dimension. The first axis may preferably be substantially parallel to the second axis, or substantially perpendicular to it.
In some preferred embodiments of the present invention, the structure has a second configuration, in which the structure is relatively narrow and elongated. Preferably, the structure in its narrow, elongated configuration has a long axis that is substantially parallel to an axis defined by the long dimension of the elongate probe.
In preferred embodiments of the present invention in which the structure, in its substantially rigid configuration, has the shape of a ring, the elongate probe may preferably include an external sheath, defining a central cavity, and the ring is preferably constructed so as to be withdrawn into the central cavity and thus compressed into a narrow, elongated configuration.
In preferred embodiments of the present invention in which the structure includes a hollow tube, a straight stylette is preferably provided for insertion into the center of the hollow tube, so as to cause the hollow tube to assume a straight shape. Preferably the structure includes a distal tip, and the elongate probe includes a socket in its side, so that the distal tip of the structure engages the socket when the structure assumes its substantially rigid, ring-shaped configuration. More preferably, the distal tip of the structure includes a first electrical contact, and the socket in the side of the catheter includes a second electrical contact; and contact between the first and second electrical contacts is measured so as to verify that the distal tip has engaged the socket.
In preferred embodiments of the present invention that include arms made up of substantially rigid segments and flexible joints, straightening the joints preferably causes the segments to maintain a substantially parallel alignment with an axis parallel to the long dimension of the elongate probe.
In preferred embodiments of the present invention in which the structure includes arms that protrude from the elongate probe through openings in its outer surface, the probe preferably further includes one or more lumens, and the structure has a second configuration in which the arms are held inside the one or more lumens.
Preferred embodiments of the present invention further provide that at least one of the one or more position signal generating devices is fixed in a known relation to the position of the structure in its substantially rigid configuration. Preferably at least one of the one or more position signal generating devices is fixed to the distal end of the elongate probe.
Preferably the position signal generating device comprises one or more coils, which generate position signals in response to an externally applied magnetic field. Preferably at least one of the coils is coaxial with an axis defined by the long dimension of the elongate probe.
Preferably at least one of the one or more position signal generating devices generates six-dimensional position and orientation information. Alternatively, the one or more position signal generating devices include, at least two devices for generating three-dimensional location information, placed in a mutually spaced relation. One of the one or more position information generating devices may be associated with each of the sensors.
Alternatively, the one or more position signal generating devices may include at least one device that generates three-dimensional location signals, and at least one device that generates angular orientation signals. Preferably, the at least one device that generates angular orientation signals is a rotation measuring device. This rotation measuring device may generates information regarding the rotation of the catheter about an axis defined by the catheter""s long dimension. Alternatively or additionally, the device may generate information regarding deflection of the distal end of the catheter.
Preferred embodiments of the present invention provide that the sensors be adapted to detect electrical impulses in the endocardium, where, preferably, the sensors are electrodes adapted to be placed in contact with the endocardium.
Alternatively, the sensors may be adapted to detect electrical signals in the brain, or the sensors may be ionic sensors.
Preferred embodiments of the present invention further include signal processing circuitry, which receives and processes position signals from the probe, so as to determine the positions of the physiological sensors. This signal processing circuitry is preferably further or alternatively adapted to measure a vector relating to the physiological activity.
There is further provided in accordance with a preferred embodiment of the present invention, apparatus for measuring physiological activity, including an elongate probe for insertion into the body of a subject, which probe includes a plurality of physiological sensors, which generate signals responsive to the physiological activity; and signal processing circuitry, which receives and processes physiological signals from the probe, so as to measure a vector relating to the physiological activity.
In accordance with a further preferred embodiment of the present invention, there is provided apparatus for measuring physiological activity including elongate probe apparatus adapted to detect electrical impulses in the endocardium, as described above, and further including signal processing circuitry, which measures an electrical activation vector in the heart.
Furthermore, in accordance with other preferred embodiments of the present invention, there is provided apparatus including a first elongate probe adapted to detect electrical impulses in the endocardium, as described above; and a second elongate probe, having a distal end, which is inserted into a human body, and a device that generates position signals indicative of the three-dimensional location of the distal end of the second probe. Preferably, the second elongate probe is adapted to be substantially fixed in a chamber of the heart, and the position signals generated by the device indicative of the location of the distal end of the second probe define a reference frame relative to which the position and orientation of the structure of the first elongate probe are determined. Preferably the second probe is adapted to be substantially fixed adjacent to the apex of the heart.
There is further provided in accordance with a preferred embodiment of the present invention, a method for mapping electrical activity in the endocardium of a heart, including:
inserting a catheter, having a distal end, to which a structure having a substantially rigid configuration is connected, and to which structure a plurality of sensors are fixed in known positions, into a chamber of the heart, so as to bring the sensors into contact with a locus in the endocardium;
receiving electrical signals indicative of electrical activity in the endocardium at the plurality of sensors;
determining the respective position of the sensors using position information generated by one or more position information generating devices fixed in known relation to the sensors.
Moreover, there is provided in accordance with another preferred embodiment of the present invention, a method for mapping electrical activity in the endocardium of a heart, including:
inserting a first catheter, having a distal end, to which a structure having a substantially rigid configuration is connected, and to which structure a plurality of sensors are fixed in known positions, into a chamber of the heart, so as to bring the sensors into contact with a locus in the endocardium;
inserting a second catheter, having a distal end, to which a device that generates three-dimensional location information is connected, into a chamber of the heart, so as to fix the distal end of the second catheter in a known, predetermined position in the chamber of the heart;
receiving electrical signals indicative of electrical activity in the endocardium at the plurality of sensors;
determining the respective positions of the sensors relative to a reference frame defined by the second catheter, using position information generated by one or more position information generating devices fixed in known relation to the sensors.
Preferably, in either of the above methods, the structure is inserted into a chamber of the heart by passing the structure through a blood vessel, and during insertion, the structure assumes a second configuration, which is narrow and elongated so as to pass easily through the blood vessel.
Preferably the electrical signals and the position information in accordance with the above methods are used to determine an activation vector at the locus. Preferably the vector is determined by measuring activation times of the electrical signals.
Furthermore, the one or more devices for generating position information preferably measure the position and orientation of the structure.
Preferred embodiments of the present invention provide that the sensors are coupled together as bipolar electrodes, and the vector is determined by measuring amplitudes of electrical signals received from the bipolar electrodes.
Preferred embodiments of the present invention further provide that the activation vector is mapped by receiving electrical signals from the endocardium and determining the respective positions of the sensors at multiple loci in the heart. Preferably the location of a defect in the heart""s electrical conduction is determined by measuring the direction of propagation of electrical impulses in the heart repeatedly at multiple locations.
There is further provided, in accordance with a preferred embodiment of the invention a catheter insertable into a body vessel comprising: a tubular body portion; at least one resilient member extending from a distal end of said tubular body portion, said at least one resilient member being adapted to bend over the outside of the distal end of the tubular portion and to extend distally from the distal end of the tubular portion.
Preferably, the at least one resilient member is adapted to bend over the outside of the distal end of the tubular portion during distal motion of the catheter in a vessel and is adapted to extend distally from the distal end of the tubular portion during proximal motion of the catheter in the vessel.
In a preferred embodiment of the invention the at least one resilient member has a rest position at which it does not extend axially from the tubular section.
In a preferred embodiment of the invention, the at least one resilient member comprises a plurality of resilient members attached to the distal end of the tubular section.
Preferably the plurality of resilient members are substantially symmetrically arranged about a longitudinal axis of said catheter.
In a preferred embodiment of the invention the at least one resilient member is comprised in a cap attached to the distal end of the tubular member. Preferably, the cap comprises a sleeve extending from a proximal end of said resilient member and attachable to said distal end of said tubular body portion, wherein at least one radial dimple is formed at a juncture between said sleeve and said resilient member.
In a preferred embodiment of the invention the at least one resilient member is constructed of an elastomeric material.
Preferably the catheter comprises at least one bump protruding from said at least one resilient member, preferably having at least one sensor fixed to said bump.
Preferably the catheter comprises at least one sensor fixed to said at least one resilient member.
In preferred embodiments of the invention the at least one sensor is selected from the group consisting of a position sensor, a six degree of freedom position and orientation sensor, a monopolar electrode, a bipolar electrode, a strain gauge and a physiological activity sensor.
There is further provided, in accordance with a preferred embodiment of the invention, a method for sensing a physiological activity of tissue inside a body organ, comprising:
inserting a catheter having at least according to any of claims 72-74 into said body organ;
sensing a physiological activity of said tissue with each sensor.
Preferably the sensors sense a physiological activity substantially simultaneously.
In preferred embodiments of the invention the physiological activity is selected from the group consisting of movement of said tissue, contraction time of a heart muscle, an activation signal of a heart muscle, and velocity of fluid flow.
There is further provided, in accordance with a preferred embodiment of the invention, a method for determining a velocity relating to physiological activity at a location in a tissue, comprising:
receiving signals indicative of physiological activity at a plurality of known positions adjacent to the location in the physiological tissue;
measuring a respective characteristic time at each of the plurality of positions using the signals received therefrom;
computing velocity component vectors along two non-parallel axes, wherein the velocity component vectors are defined by the known positions and the measured activation times; and
applying vector arithmetic operations to the velocity component vectors to determine the velocity at the location.
In a preferred embodiment of the invention each of the two non-parallel axes is defined by a respective pair of the known positions. Preferably each of the velocity component vectors has a magnitude determined by arithmetically dividing the distance separating the pair of known positions that define the respective axis of the velocity component vector, by the difference of the characteristic times between the known positions.
In a preferred embodiment of the invention and including finding one of the plurality of positions that has a characteristic time not substantially equal to the characteristic times of the other positions. Preferably the method comprises taking the position whose characteristic time is not substantially equal to the characteristic times of the other positions as a reference point for computing the velocity component vectors. Preferably, both of the non-parallel axes are taken to pass through the reference point.
In a preferred embodiment of the invention the method includes the location as a possible site of pathology when all of the plurality of positions are found to have a substantially equal characteristic times.
Preferably, the method includes determining the coordinates of the location relative to an external frame of reference.
In a preferred embodiment of the invention, where the signals are electrical signals, which are received by a plurality of electrodes at a plurality of known, respective positions.
Preferably, the method comprises fixing the electrodes at the distal end of a catheter, and inserting the catheter into a chamber of the heart of a subject, and wherein the velocity is a velocity of local electrical activation in the endocardium. Preferably, the method bringing the electrodes into contact with the endocardium, adjacent to the location at which the velocity is to be determined. In a preferred embodiment of the invention, the velocity is a measure of ionic current.
In a preferred embodiment of the invention the method comprises bringing the electrodes into proximity with a location in the brain, and wherein the velocity is a velocity of local electrical activation in the brain of a subject.
In accordance with a preferred embodiment of the invention, there is further provided a method of mapping the velocity of local electrical activation in a plurality of locations in the endocardium, comprising determining the velocity at a plurality of known locations in the tissue, in accordance with the above described method, and recording the velocity thus determined as a function of the respective known locations.